Patent GB-749433-A (GB)
Title: Improvements in or relating to photographic enlargers
IPC: G03B27/36
Filed: 1951-08-24
Abstract: 749,433. Photographic enlargers. MORLEY, L. Nov. 24, 1952 [Aug. 24, 1951], No. 19968/51. Class 98 (1). Photographic enlargers are provided with an automatic focusing movement which may be pre-set for any focal length lens by two preliminary focusing adjustments without knowing the focal length of the lens. As shown in Fig. 1, the lens board 25 and lower end of the bellows are carried by a mechanism holder 10, which may be locked on the column by a screw 27, and the head 23 and upper end of the bellows with the negative holder 26 are supported on a head carrier 16, slidably mounted on the pillar 2. A rod 3 with operating knob 4 is rotatably mounted parallel to the pillar 2 and has slidably keyed to it a sleeve 15 which is externally threaded to engage the head carrier 16. The lower end of this sleeve is freely and rotatably connected to a table 14 to move up and down therewith. The table carries a horizontal rod 12 which is fixed to a block sliding in the cam slide 11, formed in the mechanism holder 10 at 45 degrees to the pillar 2. The rod 12 also slides in a slotted bar 13, the upper end of which is pivoted at 17 to a block 18. The latter is adjustable horizontally on a worm 20 by means of a knob 21. The pivot 17 is guided by a slot 19. Fixed parallel to the bar 13 is a connecting rod 8 which is secured at one end to pivot 17 and slides at the other end in a lower pivot 9 which is formed in a holder 5. The pivot holder 5 is slidable on the column and may be clamped by a screw 6. To pre-set the focus the mechanism holder 10 is undamped and lowered onto the pivot holder 5, where it is clamped by a screw 7. In this position the rod 12 is at the top of slide 11 and the bar 13 and connecting rod 8 are horizontal. The pivot holder 5 is unclamped from the column and the two lockedtogether holders are moved together and the rod 3 rotated by knob 4 to focus the image at a ratio of 1: 1. The pivot holder 5 is then clamped and remains in the set position. The mechanism holder is then unclamped from holder 10 and raised to the top of the column, taking the head carrier 16 with it. The image is then focused in this position by rotating the knob 21. The mechanism is thus set for automatic focusing between these two extreme positions. In the modification shown in Fig. 2, the head 23 is carried on a column 36 secured to the mechanism holder 10 and its weight is supported by a spring 37. The rod 3 (Fig. 1) for adjusting the separation of the pivot at 12 and the carrier head 16 is replaced in Fig. 2 by a rod 33, made in two halves with opposed threads. A correspondingly threaded sleeve 4y connects the two portions and on turning this by means of knob 4x the link 33 is lengthened or shortened. The upper end 34 of link 33 can slide on arm 35 of the head carrier. The pivot at 12 (Fig. 1) is replaced by a pivot 30 and the cam slide is a rod 31 in a slide 32 fixed at 45 degrees to the mechanism holder 10. The worm 20, knob 21, block 18 and pivot 17 are as in Fig. 1. A bar 29 with slot 28 works over the pivot 17 and is parallel to the connecting rod 8 as is bar 13 in Fig. 1. The pre-setting operation is as in Fig. 1. It is stated that the column 2 need not be vertical but at some other angle to the base 1. In that case the cam slide (11 or 31) is not at 45 degrees to the column but at some other fixed angle.